Throttle Position Sensor

The Throttle Position Sensor (TPS) is a 3-wire variable resistor that provides the Electronic Control Module (ECM) with an input signal (voltage) that represents the throttle blade position of the throttle body. The sensor is connected to the throttle blade shaft. As the position of the throttle blade changes, the resistance (output voltage) of the TPS changes. The ECM supplies approximately 5 volts to the TPS. The TPS output voltage (input signal to the ECM) represents the throttle blade position. The ECM receives an input signal voltage from the TPS. This will vary in an approximate range of from .26 volts at minimum throttle opening (idle), to 4.49 volts at wide-open throttle. Along with inputs from other sensors, the ECM uses the TPS input to determine current engine operating conditions. In response to engine operating conditions, the ECM will adjust fuel injector pulse width and ignition timing.

Removal & Installation

Remove the air intake tube.

Disconnect the Throttle Position Sensor (TPS) electrical connector.

Remove the TPS mounting screws.

Remove the TPS.

Fig. Throttle position sensor mounting

To install:

NOTE

The throttle shaft end of throttle body slides into a socket in TPS. The TPS must be installed so that it can be rotated a few degrees. If sensor will not rotate, install the sensor with throttle shaft on other side of socket tangs. The TPS will be under slight tension when rotated.

Manually operate the throttle by hand to check for any TPS binding before starting the engine.

Install the air intake tube.

Testing

Start the engine and allow it to reach normal operating temperature. Using a diagnostic scan tool, check for the presence of any Diagnostic Trouble Codes (DTCs). Record and address these codes as necessary.

Refer to any Technical Service Bulletins (TSBs) that may apply.

Review the scan tool Freeze Frame information. If possible, try to duplicate the conditions under which the DTC set.

With the engine running at normal operating temperature, monitor the scan tool parameters related to the DTC while wiggling the wire harness. Look for parameter values to change and/or a DTC to set. Turn the ignition off.

Visually inspect the related wire harness. Disconnect all the related harness connectors. Look for any chafed, pierced, pinched, partially broken wires and broken, bent, pushed out, or corroded terminals. Perform a voltage drop test on the related circuits between the suspected inoperative component and the ECM.

CAUTION

Do not probe the ECM harness connectors. Probing the ECM harness connectors will damage the ECM terminals resulting in poor terminal to pin connection. Install Miller Special Tool No. 8815 to perform diagnosis.

Inspect and clean all ECM, engine, and chassis grounds that are related to the most current DTC.

If numerous trouble codes were set, use a wire schematic and look for any common ground or supply circuits.

For any Relay DTCs, actuate the Relay with the scan tool and wiggle the related wire harness to try to interrupt the actuation.

For intermittent Evaporative Emission trouble codes perform a visual and physical inspection of the related parts including hoses and the Fuel Filler cap.

Use the scan tool to perform a System Test if one applies to failing component. A co-pilot, data recorder, and/or lab scope should be used to help diagnose intermittent conditions.